Air conditioner duct section

ABSTRACT

AN AIR CONDITIONER OF THE OUTSIDE MOUNTED TYPE HAVING A ONE PIECE AIR CONDITIONING DUCT SECTION IN WHICH THE WALLS ARE FORMED IN A ONE-SHOT MOLDING OPERATION OF AN EXPANDED RESINOUS POLYMER PROVIDING A CLOSE CELL, RIGID, WALL STRUCTURE.

M. D. ULICH AIR CONDITIONER DUCT SECTION 2 Sheets-Sheet 1 Filed-Dec. 5, 1968 1 (III -.Jan.s, 97 .D.U'UCH 3,552,139

AIR CONDITIONER DUCT SECTION I Filed ec; 5, 1968 2 Sheets-Sheet 2 I I I FIG.5.

United States Patent Ofiice 3,552,139 Patented Jan. 5, 1971 ABSTRACT OF THE DISCLOSURE An air conditioner of the outside mounted type having a one piece air conditioning duct section in which the walls are formed in a one-shot molding operation of an expanded resinous polymer providing a close cell, rigid, wall structure.

CROSS REFERENCE TO RELATED APPLICATIONS Related US. patent applications are Oberdier, Serial, 'No. 781,518 entitled Outside Mounted Room Air Conditioner Structure (W.E. 40,288) and Ulich Serial No. 781,516, entitled Outside Mounted Room Air Conditioner (W.E. 40,297).

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to the art of air conditioning.

Description of the prior art So far as I know, no air conditioner having a duct section according to the invention has been previously made or suggested in the prior art. The desirability of providing a duct section according to the invention arose in connection with the development of a premium type room air conditioner of the kind which includes a main section which is positioned wholly outside a building and depends along the building wall below a window opening and which is connected to the building window opening by means of a duct section whichprovides passages for circulating air between the room being conditioned and the main section of the air conditioner.

It is desirable that a duct section in this environment possesses certain characteristics. Since the air passing through the duct section is relatively cool as compared to the atmosphere about the exterior of duct section, both the exterior walls and the inter-mediate wall dividing the section into two separate passages, should be of a character limiting heat conductivity through the walls. The walls should not be unduly thick since the air flow passages should have sufficient cross sectional area to accommodate the required air flow without too much resistance. The overall dimension of the duct section normal to the direction of their flow, should be kept to a reasonable minimum to avoid occupying too much space in the window. Since the exterior of the duct section is exposed to the weather, it should be reasonably weatherable. Further, the exterior of the duct section should be able to take a reasonable amount of abuse in handling and as installed. Since the depth of the duct section in the direction of air flow will be different in different installations depending upon the type of building and window construction, it is desirable that the duct section be of a nature that it may be cut to size by a customer having no special skill and no special tools other than those which may be reasonably and economically provided with the air conditioner itself. Finally, the ductsection must be of the character that its cost is not unreasonable.

SUMMARY OF THE INVENTION A duct section according to the invention meets the desiderata listed above. The duct section is molded as a one piece structure having walls forming a pair of closed passages for the length of the section, the section being molded of an expanded resinous polymer such as polyurethane or polystyrene providing rigid, closed cell, wall structure. When polyurethane is used, the walls have cores of low density, and an integral skin of a density in the order of about five times that of the cores.

DRAWING DESCRIPTION FIG. 1 is a side elevational view of a room air conditioner having a duct section according to the invention in installed position;

FIG. 2 is an isometric view of the inner face of the main section of the room air conditioner of FIG. 1 illustrating the open upper portion of the interior face of the main section of the room air conditioner to which the outer end of the duct section is ultimately connected;

FIG. 3 is an isometric view of the duct section and illustrating how the duct section is cut to the proper depth for particular installations;

FIG. 4 is a fragmentary isometric view of the lower left-hand corner of the inner end of the duct section and illustrating how the control box for the room air conditioner and its associated service cord are accommodated by the duct section;

FIG. 5 is a slightly exploded view in the nature of an end elevational view of a mold in which the duct section may be formed; and

FIG. 6 is a fragmentary sectional view of a piece of a wall of the duct section.

DESCRIPTION OF THE PREFERRED EMBODIMENT A room air conditioner to which the duct section according to the invention is particularly applicable is illustrated in FIG. 1 and includes a main section 10, the duct section 11 which has its open outer end attached in sealed relationship to the open upper inner face 12 of the main section, and a decorative front 13 attached to the open inner end of the duct section.

The main section is of generally rectangular, boxshape and is designed to depend along the outside of a building wall 14 below a window opening 15 in the building wall. The window assembly illustrated is of the typical single or double hung wooden type and includes a window sash 16 which is vertically movable in the sash tracks, and the window sill 17.

The main section 10 contains the refrigeration system components and the air flow components which together contribute most of the weight of the unit. The locations of these components within the main section are designated by the dashline outlines in FIG. 1 and include a refrigerant compressor 18, condenser 19, and a condenser fan 20 driven by electric motor 21, all of these components enumerated being in the lower part of the main section as illustrated. The upper part of the main section contains a pair of fans in housings 22 driven by an electric motor 23 positioned between the fan housings, a refrigerant evaporator 24, duct work 25 leading from the fan housing discharge to the upstream face of the evaporator. The motor capacitors and other electrical control components (not shown) are located between the fan housings and duct work adjacent the outer face 26 of the main section.

The duct section 11 (FIGS. 1 and 3) is a one piece structure molded in a one-shot operation of a resinous polymer expanded in the fabrication process and then cured to form walls of a rigid, closed cell character. The flared, open, outer end 27 of the duct is adapted for connection in substantially sealed relation to the upper, inner face portion 12 of the main section. The open inner end 28 communicates with the room being conditioned through the open-work decorative front 13 (FIG. 1). As shown, the duct section is generally of a rectangular box shape throughout most of its depth and includes upper and lower walls 29 and 30 and opposite side walls 31 and 32. The outer end portions 33 and 34 of the upper and lower walls, respectively, diverge from each other as shown. An intermediate wall 35 separates the interior of the duct section into a lower, return air passage 36, and an upper, conditioned air passage 37, and includes an outer marginal portion 38 inclined downwardly to generally parallel the flared portion 34 of the lower wall. Thus, the lower passage is of substantially uniform cross-section area from the inner end to the outer end of the duct section, while the upper passage has a mouth with a cross-sectional area about half again as great as the area of the upper passage itself. The lower passage is about a third larger at its inlet end than the upper passage at its outer end. The open mouth of the upper passage is sized to fit over the downstream face of the evaporator 24 (FIG. 2), which occupies the upper part of the open, upper portion 12 of the inner face of the main section 10. The outer end of the lower passage connects to the remainder of the open area and the downwardly inclined margin 38 of the intermediate wall aids in directing the return air down toward the inlets of the fans in the main section.

The manner in which the room air conditioner is mounted to the building is described fully in my copending patent application noted before. It will sufiice for here to point out that the duct section is substantially non-load bearing with respect to the weight of the main section 10, and that the duct section is attached to the main section by spacer screws 39 (FIGS. 1 and 2) which are turned into the duct support brackets 40 fastened to t the main section. The installed depth of the duct section (inner to outer end dimension) is determined in accordance with the depth of the building wall and sill projection relative to the location of the window, so that normally the duct section must be cut to obtain a proper fit of its inner end with the decorative front thereon in the window opening. With a duct section according to the invention, this cutting operation may be performed as illustrated in FIG. 3 in which a scoring or cutting blade 41 at the end of an inexpensive adjustable gauge 42 may be used. The gauge is set for the removal of the proper amount of the inner end portion of the duct and is then drawn along both the interior and exterior faces of the four exterior walls 2932, and also along both the upper and lower faces of the intermediate wall 35, v

and the waste portion of the duct is then simply removed or snapped off to leave a relatively sharp, straight edge upon which the decorative front seats.

Before the duct section is attached to the main section, and after it has been sized, the control box 43 (FIGS. 2 and 4) is mounted in the lower left front corner of the duct section by several screws which are turned up through holes drilled in specified locations in the bottom wall 30 of the duct section and the service cord 44 is laid in place in the groove 45 in the bottom wall of the section. The portion of the service cord extending out past the front edge of the duct is accommodated by a special channel (not shown) extending along the bottom edge of the decorative front.

The exemplary duct section illustrated herein for particular application to the room air conditioner shown is formed in a mold of the general character illustrated in FIG. 5. That view is in the general nature of a vertical section, but is taken on a vertical plane corresponding to the inner face of an end wall, and the separable parts of the mold are shown in slightly separated relation with arrows indicating the direction the parts are moved to close the mold. The trapezoidal frustums 45 and 46 are fixed to the base 47, and extend in length for the same distance as the dimension measured between the inner faces of the side walls 31 and 32. The interior core 48 forms the upper passage of the duct, while the core 49 forms the lower passage, and its lower portion 50 is complementary in shape to the frustum surface 46 to form the angled outer end of the lower passage. Both the cores 48 and 49 are of the same length as the frustums. The frustums 45 of course forms the mouth of the upper passage.

The exterior side wall 51 of the mold is attached along its one vertical edge to one exterior end wall (not shown) of the mold. While the other exterior side wall 52 is attached along one of its vertical edges to the other exterior end wall of the mold. Thus, as viewed from above, each of the end wallside wall sets forms an L- shape, and each set is disposed to face in complementary relation the other of the sets to enclose the rectangular outer enclosure within which the duct is formed. The top 53 of the mold is substantially planar and includes pour holes 54 (3 shown as an example) through which the components of the polyurethane material are introduced into the mold. The top wall also includes a number of vent holes (8 for example, none shown) which are substantially smaller than the pour holes. The pour holes are plugged after the foam material is introduced into the mold from the foam nozzle assembly 55. The mold assembly also includes braces and means for holding the mold parts together, but these are not shown since they may take any of the conventional forms.

The surfaces of the mold against which the foaming occurs are preferably of a polished metal to facilitate parting when the mold is removed. A satisfactory mold for purposes of making prototype duct sections of polyurethane has been constructed of laminated plywood with the mold surfaces being thin aluminum sheets polished on the faces against which the foam is directed. Additionally, the walls which appear to be approximately parallel may have a slight amount of draft in them to accommodate parting. Polyvinyl alcohol, which is inexpensive, easily sprayed and water soluble, serves as a satisfactory parting agent applied to the surfaces against which the foam expands. It will be appreciated that for production runs a more durable mold material such as cast aluminum with polished surfaces is used.

The selection of a particular polyurethane foam system and the controlling variables during the foaming and curing operations is dependent upon the exact characteristics desired in the final product. In that connection, some of the characteristics I recognize as desirable include a relatively low density core of the duct wall sections in the order of four to six pounds per cubic foot to provide good thermal insulation, a relatively smooth solid integral skin having a density in the order of five times that of the core for appearance and weatherability, the overall density being in the order of about ten pounds per cubic foot, and the thermal conductivity of the walls having a K factor in the order of 0.15 to 0.20 B.t.u.-inch/sq. ft./h0ur/F.

One satisfactory foam system commercially available from Pittsburgh Plate Glass Company has as its main components a polyol identified as No. 6500 SCl42 and an isocyanate identified as No. 6409. This system under a free-rise condition would provide an expanded foam having a density of about 5 pounds per cubic foot. The volumetric ratio of the polyol component to the isocyanate is about 1 /2 to 1, and the fluorocarbon 11 component used as the blowing agent is about 14% by total weight. The polyol temperature is maintained at about F., while the isocyanate temperature is maintained at about F., and the mold at about F. The total weight of the material introduced into the mold is about two to two and one half pounds so that if it were permitted to have a free rise it would expand in volume to about one hah cubic foot. However the mold volume is only about a fifth to a sixth of a cubic foot, and accordingly the material undergoes a proportional degree of packing as it expands.

The rpresentation of FIG. 6 is intended to illustrate in somewhat diagrammatic fashion the general appearance of a cross section through a wall of the duct made of polyurethane. The integral skin surfaces 60 are represented as solid lines indicating relatively high density as compared to the core 62. In an actual sample cross-sectional area taken through a wall according to the=invention, the line of demarcation between the skin and core is not as distinct.

It will be appreciated that variations in density, surface quality, and, cell size can be varied appreciably. US. Pat. 3,072,582 should be referred to for detailed information on compositions and techniques applicable in connection with a duct: section according to my invention. The currently preferred characteristics are considered to be a practical balance between such factors as the thermal conductivity, the total weight of material required, and time factors in the fabricating and curing. For example, if the polyurethane material is limited to that which will provide a lower core density of say 2 to 3 pounds per cubic foot, then the integral skin will accordingly be less dense with a corresponding loss of skin quality and, additionally, a longer cure time is required in a givenmold before the duct section may be parted from the mold. In this connection, a reasonably tough skin is desirable to give sufficient strength to part the duct section from the mold.

In the duct section referred to as an example, the thickness of thefwalls may be about to /2 of an inch thick, to width ofthe section is about 25 inches, and the depth of the section ,from its inner to outer end before cutting is about 8 inches. A preferred completed duct of polyurethane weighs about two to two and a half pounds. Suitable additives may be provided to make the walls self-extinguishing, as is conventional.

The same general mold arrangement may be used when the duct section is to be formed of polystyrene, but with the conventional changes to accommodate the well known differences in fabricating. The steps in molding articles of polystyreneare conventional and well known in that art, and accordingly may be applied to the fabrication of the duct section.

Expandable polystyrene is readily available commercially in bead form incorporating a volatile blowing agent such as pentane. The currently preferred material has a non-expanded density of about 10-11 pounds per cubic foot. These beads are preexpanded with heat to reduce the density to about 8.5 pounds per cubic foot, and are conveyed by air pressure into the mold to fill the mold. Then the mold is heated further to continue the expansion of the beads and fuse them together and form relatively smooth wall surfaces. The duct section walls formed of polystyrene do not have a skin which is materially different in density than the remainder of the wall. Also at the density suggested as an example, the lack of selfextinguishing properties of the polystyrene is such, that one or more fire retardant coatings on the wall surfaces is required.

I claim as my invention:

1. The combination of a room air conditioner having a main section adapted for positioning outside the building to extend down along the building wall below a window in the wall, and a separable duct section extending between the upper portion of said main section to the window, said main section containing substantially all of the refrigeration and air flow components of said room air conditioner, said duct section being a one-piece, integral, molded member having four outer walls, and an intermediate wall dividing the interior of said duct section into separate passages, and being made of a resinous polymer expanded to form walls of closed cell, rigid foam structure having a thermal conductivity K factor less than about 0.5 B.t.u.-in./hr./ft. /F.

2. The combination of claim 1 wherein said resinous polymer is polyurethane.

3. The combination of claim 2 wherein said walls comprise interior low density core portions having a density of about 4-6 pounds per cubic foot, and integral, relatively high density, thin, skin portions a density of about five times that of the core portions.

4. The combination of claim 1 wherein said resinous polymer is polystyrene.

5. A one-piece air conditioning duct section providing two separate passages for connecting a building space to be conditioned and an air conditioner positioned outside said building space, said duct section being formed of a one-shot molded resinous polymer expanded to provide walls for said passages of rigid, closed cell foam character and having a thermal conductivity K factor less than about 0.5 B.t.u.-in./hr./ft. /F.

6. A duct section according to claim 5 wherein:

the outer end of said duct section includes end portions of at least two of said walls opposite each other diverging from each other to form a mouth for at least one of said passages.

7. A duct section according to claim 6 wherein:

the outer end portions of an outer wall and an intermediate wall form said mouth, and the outer end portion of the other outer wall opposite the first mentioned outer wall is disposed generally parallel to the outer end portion of the intermediate wall, so that one of said passages is substantially uniform in cross-sectional area from end-to-end, while the other of said passages has an enlarged mouth at its outer end.

v8. A one-piece air conditioning duct section comprising walls forming at least one perimetrically closed pas-- sage for the length of the section, said walls being formed solely of rigid, closed-cell, molded polyurethane foam having a low density core and an integral skin of a substantially higher density and having a thermal conductivity K factor less than about 0.5 B.t.u.-in./hr./ft. F.

References Cited UNITED STATES PATENTS 2,939,297 6/1960 Karger 62262 2,989,855 6/1961 Thompson 62262 3,465,539 9/1969 Smith 62-262 WILLIAM J. WYE, Primary Examiner US. Cl. X.R. 98-94 

